1. Field of the Invention
The present invention relates to a conductive paste for internal electrodes, a multilayer ceramic electronic component using the same, and a method of manufacturing the same.
2. Description of the Related Art
As electronic components using a ceramic material, there may be provided a capacitor, an inductor, a piezoelectric element, a varistor, a thermistor, and the like.
Among these, a multilayer ceramic capacitor (MLCC), a condenser having a chip shape, has advantages such as compactness, high capacitance, and ease of mounting, and may be easily installed in printed circuit boards of various electronic products such as personal digital assistants (PDAs), cellular phones, and the like, to perform an important role in charging electricity therein and discharging electricity therefrom. MLCCs have various sizes and stack structures according to intended use and desired capacitance thereof.
Recently, in accordance with the trend for small, slimmed electronic products, a multilayer ceramic capacitor, an essential passive component in electronic products, has also been required to have a subminiaturized size and super high capacitance.
Therefore, a multilayer ceramic capacitor in which a dielectric layer and internal electrodes are thinned for the subminiaturized size, and increasing amounts of dielectric layers and internal electrode layers have been stacked in order to realize super high capacitance has been manufactured.
In the multilayer ceramic capacitor, barium titanate (BaTiO3) is generally used as a material for dielectric layers, and nickel is commonly used as a material for internal electrodes. Here, it is necessary to use particulate barium titanate and particulate nickel powder having high crystallinity for a product having a subminiaturized size and high capacitance.
The multilayer ceramic capacitor may be manufactured by stacking layers of internal electrode formed on ceramic sheets and performing a co-firing process at a temperature of 1000° C. to 1200° C. for densification of the ceramic sheets. However, a particulate nickel powder may be over-fired, resulting in particle-growth, such that the thickness of the internal electrode may be increased, causing a limitation in producing a small, slimmed product. In addition, since a large gap may be formed between the internal electrodes to cause a disconnection phenomenon in which the internal electrodes are disconnected from each other, internal electrode connectivity may be deteriorated, and capacitance may be decreased.
In addition, a nickel powder particle may have a large surface area, high activity, and a significantly low sintering initiation temperature. In particular, in the case of performing the sintering process under a non-oxidation atmosphere in order to prevent the oxidation of nickel, the internal electrode formed of nickel is initially sintered and shrunk at a low temperature of 400° C. or less; however, the ceramic sheet having a relatively higher sintering temperature is not sintered and shrunk.
Therefore, at the time of the sintering process, shrinkage behaviors of the ceramic sheet and the internal electrode may be different, to thereby generate a relatively large amount of stress in the multilayer ceramic capacitor, such that structural defects such as delamination, cracking, and the like, may be generated in products, leading to deteriorated productivity in a multilayer ceramic capacitor manufacturing process.
In order to solve the problem, nickel powder particle surfaces may be coated with an oxide.
However, in this case, the oxide may react with the ceramic of the dielectric layer to obtain an additional effect in changing ceramic characteristics. In addition, when a coating layer is formed around the nickel particles which are not completely dispersed but are agglomerated, since shrinkage is initiated in the nickel particle present in the coating layer at an original low temperature, the coating layer may be destroyed and the sintering process may rapidly progress, such that the oxide may be extruded to the outside of a sintered body. As a result, an effect of suppressing the sintering of the nickel may not be sufficiently obtained.